Compilare: user.cpp: In function ‘int main()’: user.cpp:175:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k>=m[j].size()) ^ user.cpp:69:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("multisum.in","r",stdin); ^ user.cpp:70:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("multisum.out","w",stdout); ^ user.cpp:71:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&c); ^ user.cpp:124:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&x,&y); ^